Congratulations! well, that makes up for the draw against the 1800 - and a bit more.
The opening: you are right, Nbd2 is not good. However, I would not have found dxc4, Nxc4, c5, because it is "to take is a mistake".
However, there are 2 guidlines I know in this Catalan-set-up:
The queen on c2 feels uncomfortable if you push ...c5, even in the slav. However, it is psychologically not easy to find c5, because the pawn just moved to c6, and thus is felt like a tempo loss.
However, if black had played Tarrasch-similar lines, the queen had not gone to c2 in the first place. So kind of "refutation light" is to go for c5 even in the slav (if there is a Qc2).
Some other expert played against me ...Nb8-a6. This is also an interesting approach. It aims for an eventual Na6-b4, attacking the queen. I dont think it is a good as Rc8 and c6-c5 in general, but needs to be kept in mind and dependend on the position, you might want to go for Nb8-a6.
If the white queen is on c2, I try to delay the placement of my Nb1. If you look at other Super-GM games (especially your dutch Super-GM Giri, the Catalan-expert), they tend to want to delay the development of the Nb1.
The "signal" to develop the Nb1 is for me: where is the Bc8 going to?
If the Bc8 is going to b7, then the Nb1 is better jumping to c3, where it acts more towards the center.
If the Bc8 is going to a6, then the Nb1 is better placed on d2, where it guards c4.
So this is how a Catalan is ideally played in my opinion:
After that, it depends what you want to play later: Bd6 or Be7?
I think Bd6 with e6-e5 is simplest to equalize.
If you place it on ...Bb4-e7, you should later not capture on e4 with d5xe4 (after white pushed e2-e4, which is the whole purpose of the Qc2 placement).
However, if white then playes e2-e4, you must not have blocked the e8-square with a rook (Rf8-e8 is bad if you dont have played Bd6 but Be7. The e8 square is needed for the Nf6 to retreat when e2-e4 is played).
All in all, I guess Bd6 is so much simpler to play with black. Then Re8 and even Qe7 can sometimes be played before you open with e6-e5.
Since in above variation there is likely no Nbd2 placement anymore in most games (but instead it is often played to c3), you will most often play your Bc8 to b7. But really, the Bc8 should move according to what the white Nb1 is going to do.
YEAH, I beat a 2347 FM! He is the number 1 rated at my local club. I am now leading the internal competitition!